Field of the Invention
The present invention relates to radiation dosimetry and more specifically to high sensitivity radiation dose semiconductor sensors for occupational dosimetry.
Related Art
The United States, as well as many other countries, requires employees who work with sources of ionizing radiation to be monitored by a federally-accredited program. Occupation dosimetry, as it is called, covers millions of radiation workers in healthcare, mining, the nuclear power industry, etc., and monitors the long-term exposure to potentially-harmful doses of ionizing radiation. Typical applied doses range from 0.1 mSv to 50 mSv (or 0.01 Rem to 5 Rem). The maximum whole-body dose allowed in the United States is 50 mSv per year. This needs to be measured above the background radiation (average of about 3 mSv per year) that the user receives to determine what dose received was occupational.
Capacitive radiation sensors, in particular semiconductor-based capacitive radiation sensors, such as radiation sensitive MOSCAP sensors offer high sensitivity and measurement resolution and are therefore relevant in radiation dosimetry application. In occupational dosimetry, an effort needs to be made to ensure that the sensor responds or receives radiation in the same way as human tissue. One demonstrated way is by placing filters over a series of sensors to attenuate signal at different energy levels, and use a weighted sum of the outputs to approximate tissue equivalence of the sensor radiation response. As a consequence the performance of the sensor may suffer as these filters, limit the measurement sensitivity of incident radiation by variably attenuating the radiation signal based on incident photon energy. Additionally, the filters that would otherwise be used to obtain tissue equivalence are large and prevent miniaturization of circuitry while making measurement more complicated.